Gas burner



Jan. 30, 1945.

F1a. 2 A

H. R. MA-xoN, JR

GAS BURNER Filed May 2e, 1945 FIG'. 1

3 Sheets-Sheet l i ifi mwen-rok.l BY v HARRY R. AXUNJR A TTORNEY Jan.30, 14945.

H. R. MAXONy JR GAS BURNER Filed May Q6, 1945 3 Sheets-Sheet 5 yIYENTOR.- HARRY R. MAXON. ';JR

ATTORNEY Patented Jan. 30, 1945 GAS Buisman Harry R. Maxon. Jr., Muncie,1nd., assignor to Maxon Premix Burner Company, Muncie, Ind., acorporation of Delaware Application May as, 1943, serial No. 438,791

e claims. (ci. 15s-L7) In operations of heat treating wherein a widerange of furnace temperatures is required, there has long --been theproblem of how best to obtain, and of how best to control heat inputs.

One of the many problems which vhave confronted the designer of aninstallation for heat treating of metal, is the securing of adequateturn down range in the burnerl system. By burner system being ymeant,the lburner or burners u sed in connection with a furnace, or furnaces.Such problem is especially present in the handling of a batch-typefurnace, because of the `following factors:

A. The burner system must have a sufficiently large maximum capacity toprovide adequate speed of heat input for initially 'bringing the chargeof metal pieces to be treated, up to desired control temperature.

lthe installation of duplicate heat treating furnaces or ovens inthousands of plantsthere having been no choice other than to install oneiurna'ce for' suchoper'ations as fall rin the 1500 to 1-700 degreerange, and also to install -a different furnace for heat treatingoperations that fall B. The burner system must have a sufficiently lowminimum capacity to prevent overheating* after the control temperaturewill have been' reached. Such conditions may require a minimum firingrate as low as one eighth of the maximum burner .capacity (particularlywhen the charge of metal pieces is held inthe furnace for a soakingperiod of several hours after the desired temperature will have beenreached).` Under conditions as above indicated, it is understood thatthe lburner system must have a turn down range of 8 to 1. That is tosay, there must be an 8 to 1 ratio between' the maximum and the minimumring rates. y

C.- 'The burner system must be suflcientlyflexible to permit ring of the-furnace or oven at more than one control temperature. For examwithinthe 800 to 1200 degree range. Resultant, r

in many instances, has been a duplication of `capital investment,especially undesirable in plants where nances are limited, and whereheat treating operations are only occasional.

Many plants are out of balance in their heat treating facilities, havingan excess of furnaces for high temperature operations, and at the sametime, being inadequately equipped for operations wherein drawing,tempering, or stress relieving,

ple, steel parts to .be treated, are frequently heated to atemperaturewithin the range of 1500 -to 1700 degrees and then suddenlyquenched in oil or Water to impart characteristics of additionalhardness to the metal. It is customary, after the steel will thus havebeen hardened, to reheat same to a temperature within a range of 800 to1200 degrees, for the drawing out ofundesirable stresses or strainswhichmay have been set up during the quenching operation.

Hitherto it has been found impossible to obtain suillcient burnerilexibility to permit of the handling of both of the above namedoperations l that is, to quench at 1500l to 1700 degrees, and to draw at800 to 1200 degrees) in the same furnace without shutting off part ofthe lburners,

and thus impairing uniformity of heat distribution. There is needed, foroperationsV at' 1700 degrees, approximately five times as much heat inthe 800 to 1200 degree range are involved. Conversely, numerous otherplants may be pos, sessed of large and costly facilities for vthe lowtemperature work, but are acutely bottle necked when confronted withoperations of normalizing at 1700 degrees. f

Frm the conditions above sketched, there has developed an urgent demandfor a multiple purpose lfurnace; one that can be operated at any of thehigher heat treating temperatures, or alperatures.

In endeavors 'to meet contingencies such as ternately, at any of thelower heat treating temi those above outlined,'extensive efforts havebeen as is required for re-processing the'same mate- 55 put forth towork out a b urner system having a sufficient turn down range to make amultiple purpose furnace possible. 'Elaborate tests along this line haveindicated that to assure any practicable degreeof flexibility of furnaceoperation a burner system having a turn down range of at least 40 to 1,and preferably, 50 to 1, is required'.

For illustration, the case of a certain type of annealing furnaceoperating at 1750 degrees, may

' be cited. As hereinbefore pointed out at A, the burner system must belarge enough whereby to bring the charge-of metal pieces rapidly up tothe. desired 1750 degree control temperature, and

which in this instance requires a maximum ring rate of 2,400,000 B. t.u. per hour. A't the same time, as pointed out in"B above, the burnersystem just mentioned must be capable of throttling low enough (usuallya turn down cf` 8 to 1) to avoid overheating during the soaking period.That is to say, that while the charge in the car-type 4furnace citedabove is lbeing soaked at 1750 degrees control temperature, the actualheat input required, may drop so low that the.

burner firing rate is only 300,000 B. t. u. per hour, or one eighth ofmaximum.

Now let it :be assumed that the above charge of metal (or an equivalentcharge) be placed in the aforesaid furnace, for drawing or tempering at800 degrees. At this lower temperature, the maximum burner firing raterequired for bringing the charge quickly up to temperature may be (asoutlined in C above) as little as one fourth, or even one fifth, of theprevious maximum firing rate. That is to say, the actual heat inputrequired for bringing the charge quickly up to the desired 800 degree'temperature will -be approximately 480,000 B. t. u. per hour. But offar greater importance, the minimum firing rate required of the burners,in order to prevent overheating the charge while soaking at 800degrees.-

must |he as low as 60,000 B. t. u. per hour W; of the 480,000 B. t. u.per hour maximum firing rate).

It will thus be seen that the burner system for the furnace just cited,must have an overall maximum of 2,400,000 B. t. u. per hour (for plentyof speed of heat input at 1750 degrees), and it must have an overallminimum as low as 60,000 B. t. u. per hour (to avoid overheating whenhold' ing at 800 degrees), or a combinedoverall turn down range of 40to 1. v

The car-type furnace above mentioned is typical of a large variety ofheat treating furnaces now :being designed for multiple purpose service.In each ofsuch cases, the burner systernmust have a turn down range ofat least 40 to 1. If the,furnace is to be equipped with automatictemperature control (as a very high percentage of recent installationsare), a still wider turn-down range on the part of the burner system, isrequired.

Modern devices for automatic temperature control in industrial furnacesrequire, that in order to provide a margin of safety for the automaticand piping, and also preventing the burner from being throttled toextreme low firing rate.

Blowing away or the flame, and therefore the prevention of operation athigh ring rates.

Failure to hold name continuously throughout tum down.

impossibility of throttling smoothly in cases where double burners areused (a larger burner being used for handling higher heat inputs, and asmaller burner being used for handling low and minimum heat inputs),there being either a sudden gap between the minimum of a large burnerand the maximum of a small burner, or else a sudden step up or a suddenstep down at that 4phase of the throwing range at which the two firingrates overlap.

To 'the end that above named disadvantages may be overcome, and thatthere may be rendered practicable the utilization of a single furnacefor heat treating operations wherein wide ranges of temperatures arerequired, the object of my invention is to provide a burner device whichwill afford a scope of turn down suilicient to accomplsh temperaturecontrol over a range of ring capacities as great as 100 to 1, a range ofsuch scope being highly desirable if a single furnace is to be used inoperations alternating between low ktemperature work and hightemperature wor Accordingly, in carrying out the purposes of myinvention, further aims are to provide a burner which will lend itselfespecially to use in industrial heat treating furnaces and ovens, itbeing kept in mind that for such an apparatus, there must be, at allstages of firing rates (from low minimum to high maximum), combustionofsuch dependability and such constancy, that in throttling, the changein heat input from any intermediate capacity to another, may be smoothand even.

The above named objects, as well as other and more speciiic endeavors ofmy invention, and which have to do with improved structural featuresleading to economy of manufacture, facility of installation and use, andto efficiency vand durability, are accomplished by, and my invencontrolsystem, so that over-shooting or unf f der-shooting of vdesiredtemperature may be quickly corrected, the burner system must be capableof turning slightly higher, or turning slightly lower than is actuallynecessary for supplying A the heat input needed at any given moment. Theeiect of the above required margin of safety, is to increase the turndown requirements by an additional twenty iive per cent, thus making theovery all turn down range, for the above described furnace whenautomatically controlled, to l (inlimitation of the turn down range ofpreviously designed burners, aref Tendency of the air-gas mixture toflash back into the supply pipe, thereby limiting minimum tiring rate,such flash back damaging the burner tion is embodied in, the newconstruction, combination, and arrangement of parts illustrated in theaccompanying drawings, described in the following specification, anddened in the claims.

The several parts of the inventionare identi fied in the different viewsin the drawings, by suitable characters of reference applied to them.

In the drawings:

Figure 1 is a front'view ofmy improved gas burner.

Figure 2 isa side'view in the direction of arrow 2'in Figure 1, aportion of the mount frame being broken away, and the` mouth or inletportion of the burner block being shown in cross section.

Figure 3 is a top"plan view in the direction of arrow 3 in Figure 2,`aportion of the mount frame, and a portion of the burner block beingbroken away, and the latter being shown in cross section.l

Figure 4 is an enlarged vertical central longitu- I dinal sectional viewof Figure 2.

Figure 5 is a side view of the burner-insert, removed, the head portionthereof being shownin cross section. f y

Figure 6 is an end view in the direction of arrow 6 in Figure 5. A

Figure 'l is an end view in the direction of arrow 'I in Figure 5.

Figure 8 is a central longitudinal sectional view of said burner-insert,taken on the broken line .-8, in the direction of arrow 8 in Figure 7.

Figure 9 is an end ,view of the burner block, taken in the direction ofarrow 9 in Figure 4.

Figure 10 is an enlarged perspective view of the head portion of thesaid burner-insert.

Figure 11 is a diagrammatic view showing the location of the flame at alow nring rate.

Figure 12 is a diagrammatic view showing the location of the flame at anintermediate firing rate.n

Figure 13 is a diagrammatic view showing the location of the flame at ahigh firing rate, and its full length being not shown.

Figure 14 diagrammatically illustrates. the appearance of the inventionin a typical installation.

Figure 15 illustrates a modification.

Figure 16 is an end view of Figure 15.

The embodiment of my invention as it is described herein and depicted inthe drawings, is typical. It will be understood of course, that thedetails of construction and arrangement of parts are capable of minorchanges, alterations and modifications, such as may occur to thosepersons skilled in the' art to which the invention appertains, withoutdeparting from the spirit or principle of the inventionvor sacrificingany of its advantages. I

A metal casing I5 is provided with lateral'opening I6 in which isreceived the air inlet feed pipe I1. Forward end I8 of said casing hasinturned wall portion 20 provided with machined annular beveled seat 2I.of said casing is provided with circular opening 24. A hole in a side ofsaid casing, and which is closed by a removable plug I9, affordsfacility The rearward end portion 22 united relation as shown,constitute and end wall which is common to the outer casing I5 and tothe conduit 40, and common to the chambers thus formed, namely, the airchamber 50, and

l the internal marginal portion of the chamber 5I,

for making tests of the air pressure within the 'casing.

A metal mount frame 26, box-like in formation, embodies bulged breastportion 21 having a circular opening 28 within which the forward end I8of said casing is received, and at its annularflange 29 is secured as bythe cap screws I0. In each of thev flanges 32 and- 33 of said mountframe, is an elongated aperture 34 for vthe reception of fastener bolts(not shown) and by which the said frame is secured in its inf- -stalledposition, as indicated in Figure 14.

A hinged cover plate 31 provided at that one of the pilot holes 35 whichis in registration with the peripheral face of said shoulder is aconical recess 44. Castellated rear end 45 of said burner-insert permitsholding by a wrench when connecting the gas inlet pipe 46 at thethreaded opening therefor. A pointed set screw- 48 is so positioned,that when tightened, the burner-insert will have been tightened to andmade fast is a series of uniformly spaced ports or orifices 52. Providedin the outward or marginal area of said head portion of plate 4I of thesaid burner-insert in close proximity to, and concentric with the saidports 52, is a series of uniformly spaced ports 54 and which are instaggered rela'- tion to said ports 52. The ports 54 are of larger areathan the ports 52 and their corners are of filleted formation. Theradial partitions 55 between sad ports 54 are in alignment with thetransverse axes of said ports 52, as indicated in Figure 10. Each ofsaid partitions is of a minimum width, and all are of the minimum widthswith relation to the widths of the said ports 54, substantially as shownin Figure 10.

For reasons that are incident to convenience and economy in processing,the central mass of the head portion of said burner-insert is of bulgedformation. For the same reasons, and for the further reason, that theanterior rims of the ports-52 may be in close proximity with the planesof the ports 54, the said ports 52 are inclined at an an'gle toward thelongitudinal axis of the burner insert. Also the structural forma- Ition just mentioned simplifies the operation of drilling the ports 52 sothat they open from the gas chamber directly at the forward internalmarginal portion thereof.

A burner block 56 made of suitable refractory material such as firebrick, and which is of formation in cross section to fit into the saidmount frame 2B, is provided with a tunnel formed in circularsubdivisions or stages which are concentric and'which at their proximaledges are joined by annular oii'sets. For brevity these sub-- divisionsmay be referred to as zones, and hence, the tunnel, as zonate inlongitudinal formation.

- The said block is united with the Said mount frame, as by theapplication of high temperature cement51 at the lateral recesses 59, andat holes accordingly.

in the position indicated in Figure 4, the annular the end recess 25,the latter constituting a seal at thel forward wall of the casing I5.The mouth zone or inlet 60 of said tunnel is of diameter to closelyencircle the area' defined by a line bounding the outer series of ports54. Each of the succeeding zones 6I and 62 is of progressively largerdiameter to the discharge end of the block, and they are joined bytheannular offsets 64 and $5.l An aperture 58 which is in registrationwith the pilot hole 35 hereinbefore mentioned in connection with themount frame, extends into the zone 6I of the said tunnel, and it affordsaccess thereinto for applying a lighter' torch, or for observationpurposes. In case the block may be set so that its aperture 58 is at areverse posi-` tion, or is at a position at a right angle to that shownin Figure 3, the hinged cover plate 31v I would be fitted to a differentone of the pilot My improved burner is capable of being installed withthe casing so poised that the air feed line I1 may be either in avertical alignment, or at an angular aligment,thus accommodating itself`to local cor itions affecting the pipe lines. Illustrative of a typicalinstallation, is Figure 14. Air supply is through pipe I1,-and gassupply is through pipe 46 which is fitted with this thorough mixture inthe 'zone of a shut-ot! cock G. "The said pipes are connected withthrottling devices and regulators (not shown) usual to industrialfurnace installations and equipment.

`In operation of my new burner, the air fed into the chamber 50 nowsthrough the air ports duced along the side edges and in the space be- 1Gtween said edges and at the gas ports 52 and ahead of the partitions 55,low pressure areas, there being such an area immediately at the front ofand extending forwardly of each of said partitions. In each of these lowpressure areas there is set up a partial vacuum. The gas streams issuingfrom the gas ports 52, being sucked into said low pressure areas,collapsing, and coming' into contact with the highly agitated andbrokensurfaced streams of air, are caused to fill the space between andaround the air streams, the effect being that the gas becomes infused inand completely co-mingled with the air streams, hence the volumecomposed of all of the air-gas streams` will have become merged into anintensively and intimately mixed homogenized mass.

The mass so formed constitutes a mixture which is thorough and complete.

It is considered that the accomplishment of the 1511111181 mouth andclosely adjacent to the front of said ports is of the essence of thisinvention, the degree of thoroughness of said mixture distinguishing myimproved burner from all prior nozzle` type mixers. 3

The air and gas having not been combined until they have entered theinlet or mouth of the tunnel of the burner block, there is nopossibility of flash back such as exists with burners of the premixtype. By reason of the thorough and effec' 40 tive mixture so obtained,immediately at the said mouth 60, flame retention at minimum airpressure (that is to say, low ringrate) is assured, the tiny names, atlow pressure, burning quietly and steadily in the rst small stage orinlet zone 45 of the tunnel of the burner block, as indicated in Figure11.

As the firing rate 0f the burner is increased (incident to increase ofair pressure entering the air chamber) and the velocity of the air-gasmix- 50 ture in the mouth zone becomes too great for the continuation ofself-ignition thereat, the said mixture is discharged, unignited, beyondthe offset 64 andinto the second zone 6| of the tunnel. Tiny eddycurrents (see Figure 12) yin the air-gas 55 mixture, and which are'automatically created at the said oifset 64, whip small portions of saidmixture into the dead area. immediately at the lee of the edge of saidodset, and wherejtliey burni continuously and ignite the mass `volume ofair- 60 gas mixture issuing from the said mouth zone into the next orsecond -zone 8| of the tunnel, thus combustion is had in the remainingzones of the tunnel, or in the area or space immediately beyond theoutlet end of same, as indicated in 65 Figure 12.

Similarly, when the ring rate is still further increased, and thevelocity of the mixture is increased to such degree that ignition ceasesin the said second zone 6| ofthe tunnel, thenfat the 70 protected spaceat the lee of the edge of the next offset 65 (see Figure A12) combustionoccurs in the manner 'as above described, as indicated diagrammaticallyin Figure 13.

Whereas in most cases, atunnel or duct having furnace temperatures. Theame being constant.

and dependable at every stage of throttling, the burner accordingly isresponsive at every stage of and throughout the full turn down range.'I'he thorough and intimate mixture accomplished by my invention,occurring as it does, immediately in the mouth4 of the tunnel; andignited, as it is, at the offsets of the progressive stages of thetunnel leading to the outlet of the block, the combustion is of suchdependability and constancy that the wide range turn down so long soughtfor, is at last accomplished.

Continuous ignition and constant flame is had at all firing rates -fromlow minimum to high maximum, and without any interruption whenthrottling from one iiring rate' to the other. Because of theflexibility and the easiness of control of my improved burner it's useis not limited to any' one type of industrial furnace or oven, and itprovides advantages in a wide variety of heat applications. A eld inwhich it is especially, distinguished is the heat treating of metals inthose furnaces used for the processing of steel, aluminum or brass. Inany of said applications, the

5 ratio between the maximum and the minimum firing rates may be as greatas to 1, if desired, and the extremely wide range of turn down isaccomplished without the use of any secondary or auxiliary burners orappliances, and same is without interruption when throttlng from oneiiring rate to another.

Whereas in the preferred form of embodiment i of my invention as it isillustrated and described herein, the casing which constitutes the twochambers is of structural formation so arranged that the air isintroduced into the outer chamber,

I wish it to be understood that the invention is capable of suchmodification that when special or unusual conditions affectingprocessing of the parts, or affecting installation of the invention,might suggest a change from said embodiment, the air feed may beprovidedfor in the inner chamber, and the gas in the' outer chamber.Such a modiiication is illustrated in Figures 15 and 16, wherein 10designates the air chamber, and 'Il the gas chamber. 12 and 14 designatethe closely adjacent and staggered gas ports and air ports respectively.

What I claim as my invention is:

l. In combination with a refractory burner block having a multiple stagetunnel therethrough, each stage of progressively larger diameter fromits inlet to its outlet, and each joining span the inlet of said tunnel,is provided with av series of ports circularly arranged and which opendirectly from one of the conduits into the tunnel inlet, and is providedwith a series of ports circularly arranged in close adjacency to andalternated with the ports of the first named series,

and which said last named ports open from directly from the gas conduitinto the tunnel ina series of equally spaced circularly arranged portsinteriorly of saidconduit, and a seriesv of equally spaced circularlyarranged ports exterorly of said conduit, the ports of one series beingalternated withland in close adjacency .to the ports of the otherseries, and means to supply said gas conduit. n

5. A mixer, ignition, and combustion apparatus -consisting of a casingprovided with an air inlet,

1'0 and having an inturned forward end providedr let, and is providedwith a series of ports circularly Y arranged, equally and closelyspaced, in close adjacency to and alternated with the ports of said gasconduit, and which said last named ports open' from the air conduit intothe said.

tunnel inlet.

3. The combination of a refractory burner structure having a multiplestage tunnel therethrough, each stage of progressively larger diameterfrom its inlet to its outlet and each joining the next by an offsetshoulder, a casing embodying two conduits, one within the other,`saidcasing having a wall that terminatesveach of the conduits, is abuttedagainst said burner structure to span the inlet of said tunnel, isprovided with a series of ports circularly arranged, equally andclosely'spaced, and which open directly from one of said conduits intothe tunnel inlet, and is provided with a series of ports equally andclosely spaced in close adjacency to and alternated with the ports ofthe first named series, and which said last named ports open from theother of said conduits directly intoy said tunnel inlet, the websbetween'the ports.of one series being of predetermined form withrelation tothe forms of the ports of that series. 4. A burner apparatusof the kind described,

- consisting of a burner block having a ,tunnel therethrough, zonate information and provided I with an annular seat, said casing at its rearportion having a circular opening, a conduit exy tended into said casingand embodying at its forward end a circular transverse head plate to l5engage said annular seat, said head plate -having a lseries ofcircularly arranged radially partitioned ports therethrough exteriorlyof said conduit, and having a series of circularly arranged portstherethrough interiorly of said conduit, the ports zo of one seriesbeing alternated with and in close adjacency to the ports of the otherseries, a closure interconnecting the said gas conduit with the rearportion of said casing, inlet means for l l said gas conduit, and aburner block united with the forward end of said casing, said blockhaving a tunnel therethrough of zonate formation, the zones thereofbeing of progressively larger` diameter from the inlet to the outlet ofsaid tunnel, and the inlet zone being of diameter coincident with thatof,the head plate of said conduit.

ing of-a casinghaving an open forward end provided with an internalannular seat, and being provided at its rearward end with a circularopening, an air inlet into said casing, a conduit j having at itsforward end 'a transverse circular head plate to engage said annularseat,- and embodying at its rearward portion a shoul- 40 der to closethe said circular opening of said with a lighter aperture, a mount framein which (said block is received and secured, said frame` having abulgedbreast portion 'and provided with an opening in axial alignmentwith said casing, the said head plate having a series of circularlyarranged equally spaced ports that open therethrough exteriorly of saidconduit, and having a series of circularly arranged equally spaced portsthat open therethrough interiorly tunnel,.a casing retained at itsforward portion.

within the opening of said mount frame and abutted against the inlet endof said block, saidv casing having lan air inlet in the side thereof,and having a central opening in its rear portion, and an internalannular seat at its forward end, agas conduit which embodies at its rearportion 'an annular shoulder which' is fastened in the openingof saidcasing, and at'it's forward end a circular head plate that engages theannular seat of said casing thereby spanning the relation to thdiameters of the ports ofthat of said conduit, the portsmf one seriesbeing alternated withfthe ports of the other seriesand thel webs betweenthe ports of one of the series being radial and of predetermined widthwith series, a gas inlet means for said conduit, and a burner blockunited with the forward end of said casing and having a zonate tunneltherethrough, the inlet of which is in axial alignmentr and registrationwith the head plate of said conmiet of'said tunnel, the saidhead-platehavmg y nduit HARRY R. MAXON, Jn:

6. A gas burner of the kind described, consist-

